After victories in Virginia, Maryland, and Washington, D.C., John McCain's frontrunner status is more clearly established than ever before. His unwavering support for the war in Iraq, and for the surge, is the primary reason his once-flatlining campaign revived and prevailed.

But McCain's campaign is not the only Republican campaign that succeeded this year because of the war in Iraq. Yesterday moderate Republican Wayne Gilchrest (R-MD) was defeated for renomination by a primary challenger who based his campaign on the incumbent's opposition to the war:

What’s more, Gilchrest insists that the issue du jour in the race — his opposition to the Iraq war — is a smokescreen for the same issues that have commanded his opponents’ opposition in the past: abortion, flag-burning and gay rights...

State Sen. Richard Colburn (R), a Harris supporter who lost to Gilchrest in the 2004 primary, said Gilchrest’s opposition to the war in Iraq has given elected officials an outlet to make public their previously unofficial opposition.

Representative Walter Jones (R-NC) is also in serious trouble in his battle for renomination. Again, Iraq is the issue:

Rep. Walter Jones (R-N.C.), an opponent of the war in Iraq, is in a statistical tie with primary challenger Joe McLaughlin, according to a poll released Tuesday by McLaughlin’s campaign.

The poll, conducted by Pulse Opinion Research, shows Jones leading McLaughlin 43-41, with 5 percent supporting another candidate and 11 percent undecided.

The other Republican incumbent in serious trouble is Ron Paul. Through his entire tenure in Congress, he has served as a Republican in name, and an Independent in practice. His commitment to libertarian principles has led him to oppose a host of Republican initiatives on the grounds that they fall short of his revolutionary goals. Yet he has regularly earned renomination, usually with only token opposition. The difference this year is his vocal opposition to the Iraq war.

It has become almost unprecedented for a Member of Congress to be denied renomination. Only one incumbent Republican was defeated in a primary in the last 2 cycles. This year there may be three or more.

The strength of Iraq as an issue was unforeseen just a few months ago. It's possible that an as-yet undetected bias toward supporters of the Iraq war will play a role in the general election, as well.