Rove Is Using Threat of Loss to Stir G.O.P. By JIM RUTENBERG WASHINGTON, May 5 — To anyone who doubts the stakes for the White House in this year's midterm Congressional elections, consider that Representative John Conyers Jr. of Michigan, the Democrat who would become chairman of the Judiciary Committee if his party recaptured the House, has called for an inquiry into the possible impeachment of President Bush over the war in Iraq. Or listen to Senator Patrick J. Leahy of Vermont, who would run the Senate Judiciary Committee if the Democrats took the Senate. Mr. Leahy vowed in a...