Sen. John McCain (search) is trying to block the appointment of a union lawyer to the Federal Election Commission (search), taking on Democratic congressional leaders who recommended the attorney for the job.

McCain, R-Ariz., opposes Democratic leaders' effort to replace Commissioner Scott Thomas, a Democrat praised by campaign finance watchdogs for seeking tough enforcement of a new campaign finance law, with Robert Lenhard, associate general counsel of the American Federation of State, County and Municipal Employees. Lenhard was among those trying to have the law overturned.

Thomas' term on the commission expired last year, but he can continue in the post until he is replaced. Thomas is eligible to serve one more six-year term.

McCain wrote Senate Majority Leader Bill Frist, R-Tenn., last month and said he will object to anyone nominated to succeed Thomas. That means it would take a tough-to-achieve 60 votes for a candidate to win Senate confirmation to replace Thomas.

McCain also opposes any White House effort to replace Thomas while the Senate is in recess this summer. President Bush hasn't indicated whether he will name Lenhard or anyone.

Senate Minority Leader Tom Daschle, D-S.D., and House Minority Leader Nancy Pelosi, D-Calif., last summer recommended Lenhard as Thomas' successor. The six-member FEC includes three Democrats and three Republicans, and congressional leaders traditionally recommend people to the president to fill their party's seats.

Lenhard was among attorneys representing the AFL-CIO in its case against a new campaign finance law banning so-called "soft money" donations to the national political parties or congressional or presidential candidates. AFSCME is part of the AFL-CIO, which contended the law violates free-speech rights.

The Supreme Court upheld the law last December.