As November’s elections come into sharper focus, Democrats may have a secret weapon in their bid to keep their Senate majority: Republican candidates.

Though Democrats are on the defensive nationally, Republican candidates are encountering problems in six states that could make the difference between gaining only three to five seats or coming close to the 10 they need for control.

In Nevada, for example, embattled Majority Leader Harry Reid’s uphill re-election battle received a boost from the GOP’s nomination of Sharron Angle, a favorite of tea party groups with an array of controversial positions.

GOP woes may also help Democrats in Illinois, Kentucky and New Hampshire, where incumbents are retiring; in California, where liberal Democrat Barbara Boxer seeks a fourth term; and in Colorado, where appointed Sen. Michael Bennett faces primary and general election challenges.

Even optimistic Republican scenarios require the GOP to win virtually every marginal Democratic seat to go from their current 41 to the 51 needed for control.

Here is a look at these contests:

• Nevada: Angle has modified her pre-primary stances that angry Americans might resort to “second Amendment remedies” — a reference to the right to bear arms — and Social Security should be “phased out.” She wants to abolish the Department of Education and says Nevada should abandon its fight against burying nuclear waste at Yucca Mountain.

Though Reid remains unpopular, the fact that Nevadans can choose “none of the above” may help him.

• Illinois: Republican Rep. Mark Kirk conceded he was “careless” in exaggerating aspects of his career. They included false claims he served in the 1991 Persian Gulf War and the 2003 invasion of Iraq, ran the Pentagon war room and won an “intelligence officer of the year” award.

His claim to have been a “nursery school teacher” was refuted by the school’s director, who termed it a part-time job for a college work-study program.

Democrat Alexi Giannoulias also has problems. Regulators closed a family-owned bank after large commercial real estate losses.

• Kentucky: Republican nominee Rand Paul’s lead dropped after he said he would have opposed the 1964 Civil Rights Act as an unconstitutional infringement on private business and criticized administration pressure on BP as “un-American.”

• New Hampshire: Former state Attorney General Kelly Ayotte, who tops polls for the GOP’s Sept. 14 primary, is under fire for her handling of a fraud case that cost investors $20 million and for telling a legislative hearing she had “no personal knowledge” of what happened.

Republican and Democratic rivals said she should have taken more responsibility. But the nonpartisan FactCheck.org criticized the likely Democratic nominee, Rep. Paul Hodes, for claiming falsely in a television ad that Ayotte covered up her role by making sure her e-mails would be deleted.

• California: GOP nominee Carly Fiorina stumbled out of the primary gate with her much-publicized comment about Boxer’s hair. Her biggest handicap may be running as a conservative in a state that has consistently backed more liberal candidates, opposing abortion rights and criticizing a state climate control law backed by Gov,. Arnold Schwarzenegger to curb greenhouse gas emissions.

• Colorado: Both GOP contenders in the Aug.10 primary have encountered problems. Former Lt. Gov. Jane Norton angered conservative activists by refusing to participate in the pre-primary state convention, which endorsed tea party-backed rival Ken Buck. But Norton appeared to curry favor with conservatives by praising the “passion” and sidestepping the substance when questioners said President Obama was a Muslim and an “idiot” who wanted to let babies die alongside the road. Anti-immigration groups favor Buck for supporting a sheriff’s raid on a tax preparer’s office to identify people with false identities, a raid the State Supreme Court later ruled unconstitutional.

At present, the nonpartisan RealClearPolitics.com lists Nevada, Illinois and Colorado as toss-ups, Kentucky and New Hampshire leaning Republican, and California leaning Democratic.

Republicans are in the lead for Democratic seats in Arkansas, Delaware, Indiana and North Dakota. If most close races follow the historic pattern of joining a national trend, Republicans might win Senate control unless GOP candidates lose these potentially winnable races.

— Carl P. Leubsdorf is the former Washington bureau chief of the Dallas Morning News. carl.p.leubsdorf@gmail.com