It's not a good year to be a Republican candidate. Although the economy is robust, voters are displeased with the Bush presidency, the Iraq war and the country's direction.

The president won in 2004 because he was able to both energize and expand the Republican base. Bush did not crack into the 2000 Al Gore vote. Instead, he kept his 2000 vote (50,456,169) and found another 11,583,537 votes. The Democratic, or anti-Bush vote, rose from 50,996,116 to 59,028,109. Bush had 539,940 fewer votes than Gore in 2000, but he had 2,912,497 more votes than John Kerry in 2004.

If any portion of the Republican base, for whatever reason, declines to vote in 2006 or votes Democratic, then Republican candidates will underperform. That means that they will fall below the normal Republican vote in their district.

For those challenging Democratic incumbents, any underperformance is fatal, but for Republican incumbents or those seeking to hold the seats of retiring Republicans, a diminution of 5 percent is absorbable. However, if Republicans underperform by closer to 10 percent, that's a Democratic "wave," and a vast number of Republican candidates will drown.

Here's a look at two congressional races where Republicans, if they underperform, will lose:

6th U.S. House District (northern DuPage County and northwest Cook County suburbs): The good news for state Senator Peter Roskam, the Republican nominee to succeed retiring incumbent Henry Hyde, is that Bush won the district with 53 percent of the vote in both 2000 and 2004 and that Hyde was re-elected in 2004 with 56 percent of the vote. So Roskam can underperform slightly and still win.

The better news for Roskam is that the vaunted DuPage County Republican organization, the party's best in Illinois, is still at the top of its game. The county's state's attorney, Joe Birkett, is the Republican nominee for Illinois lieutenant governor, and the party will push hard for the Topinka-Birkett ticket, and for Roskam, in November. In the March primary, Birkett got 58,682 votes (64.4 percent) in DuPage County, and Roskam, who was unopposed for the congressional nomination, got 50,794 votes -- 44,850 in DuPage County and 5,944 in Cook County.

That's on par with Hyde's recent primary showings. Hyde, running unopposed, got 66,584 votes in the 2002 primary and 50,583 in 2004.

And the great news is that the Democrats, despite a tempestuous primary, are divided and dispirited. Iraq war veteran Tammy Duckworth eked out a 1,124-vote primary win over 2004 candidate Christine Cegelis. The total Democratic turnout was 32,575 -- 18,219 less than the Republicans'. In 2004 36,158 Democrats voted, and in 2002 turnout was 26,791.

Duckworth, a major in the Illinois Army National Guard, lost her right leg and part of her left leg when her Blackhawk helicopter was struck by a rocket propelled grenade in Iraq in 2004. She was recruited for the contest by U.S. Representative Rahm Emanuel, the Democratic Congressional Campaign Committee chairman. In the primary she was endorsed by U.S. Senators Dick Durbin and Barack Obama, and she spent just under $600,000. Almost all of her funding came from outside the district and was procured by Emanuel.

Cegelis, a liberal who got 44 percent of the vote against Hyde in 2004, thought she deserved a second shot. Emanuel thought otherwise. Cegelis ripped Duckworth as an interloper who didn't live in the district and for equivocating on Iraq. Cegelis sought a specific troop withdrawal timetable, while Duckworth backed "aggressive benchmarks."

The outcome proved, albeit narrowly, that Duckworth's mail game, which entailed seven mass mailings to Democrats, was more effective than Cegelis' ground game, which relied on precinct workers. Cegelis has given Duckworth a tepid endorsement. The final result was 14,283 for Duckworth, 13,158 for Cegelis, and 5,133 for Lindy Scott.

For November, Roskam has $800,000 on hand, he has a ground game, and he expects to spend $2 million, which will give him a great mail game. Duckworth has a major positioning problem: Does she tack to the left, ripping Bush and emerging as a get-out-of-Iraq-now candidate, thereby pacifying Cegelis' liberal base? Of does she run as a middle of the roader, supporting phased withdrawal, expecting that the liberals will back her anyway and hoping for an anti-Bush Democratic wave?

The key is Emanuel. How much will he dump into the 6th District? Duckworth can win if she defines the race as a referendum on Bush. Roskam will win if he defines the race as a contest between a local guy with local concerns versus a "celebrity" outsider being foisted on the district by Emanuel. To win, Duckworth needs to spend $3 million and inundate everybody's mailbox.

My early prediction: Hyde won this seat back in 1974, a Democratic wave year. Roskam will replicate that feat in 2006. He has money, a ground game, and local roots, and he cannot be isolated as an "extremist." The Roskam-Duckworth race is a premier contest which is critical to a Democratic takeover of the U.S. House. But if polls don't show Duckworth running even with Roskam by Labor Day, Emanuel will pull the plug and won't commit $3 million. Make Roskam the favorite.

8th U.S. House District (eastern McHenry County, western Lake County and part of northwestern Cook County): Democrat Melissa Bean was in the right place at the right time in 2004, and she unseated the complacent Republican incumbent, Phil Crane. She likely is in the same place for 2006.

The good news for Bean is that the Republicans had a mean and nasty primary, with investment banker David McSweeney emerging as the nominee. McSweeney spent $1.9 million of his own money and got 25,085 votes. The second-place finisher was attorney Kathy Salvi, who spent $1.2 million of her own money and got 19,370 votes. State Representative Bob Churchill was third with 9,169 votes.

Bean is sitting on $1.5 million in her campaign fund, while McSweeney is broke.

But the bad news for Bean is that Bush won the district in both 2000 and 2004 with 56 percent of the vote. The 2004 congressional outcome was a rejection of Crane, not an affirmation of Bean. Bush won the district by 31,535 votes, while Bean won by 9,191. In the 2006 primary, total Republican turnout was 58,456, while Bean, unopposed, got 23,375 votes in the Democratic primary.

Despite being an incumbent, Bean's Democratic support is less than solid. Turnout in the 2004 primary was 34,258, and Bean, opposed by Bill Scheurer, got 26,740 votes, or 78 percent of the votes cast. She got 26,382 votes running unopposed in 2002, meaning that she got fewer votes in 2006 than she got in 2004 and 2002. Her support of the Central American Free Trade Agreement infuriated organized labor, which was a key 2004 backer. Why is she losing votes?

Conversely, the Republican vote is stable. It was 58,450 in 2006, while Crane won the 2004 primary 35,412-16,146, in a turnout of 51,562. He got 59,051 votes running unopposed in 2002.

The 2006 Republican primary combatants were uniformly conservative, meaning for abortion restrictions, for tax cuts and against gun control. McSweeney called Salvi a liberal because she opposed tort reform and damage caps. Salvi hit McSweeney as a tax hiker because he was a Palatine Township trustee when the board increased the tax levy.

McSweeney won because he was in the race early and lined up key backing. He was endorsed by the three Cook County Republican township organizations, Palatine, Schaumburg and Barrington. McSweeney, of Barrington Hills, won those townships 7,303-4,000. He won Lake County 12,300-9,654 but lost McHenry County to Salvi 5,482-5,716.

Unlike 6th District Democrats, the 8th District Republicans are not ideologically divided. The wounds have healed, and they cannot be exploited by Bean. From a gender perspective, Salvi might have been the more formidable candidate, but McSweeney is an acceptable Republican. He can self-fund another $1 million, and he will get $1 million from Washington Republican sources.

But the key is perception. Bean wants to make the election a referendum on her tenure, as is the case with most incumbents. She has positioned herself as a moderate, independent-minded Democrat. McSweeney needs to make the election a litmus test of Republicanism and Republican "values," but not necessarily Bush support. There are many more Republicans than Democrats in the 8th District. McSweeney doesn't have Crane's baggage, but he carries Bush's burden.

If this were a 60 percent Bush district, Bean would be toast. But it's a 56 percent Bush district, with a popular female Democratic incumbent.

My early prediction: If it had been McSweeney-Bean in 2004, the Republican won have easily won. But McSweeney will underperform Bush by at least 5 percent, and Bean will have an incumbent's edge. That's enough, even against a $2 million onslaught, to make Bean a very narrow favorite.