JEFFERSON CITY • The Missouri House and Senate on Wednesday struck a deal on a congressional redistricting map, though the proposal could still face a gubernatorial veto or a court challenge.

The map, which would downsize the state's nine congressional districts to eight, differs from the most recent compromise maps proposed by the House and Senate primarily in how it divides Jefferson and St. Charles counties.

Those sticking points have been the root of intraparty squabbling between House and Senate Republicans. But factions were inspired to seek middle ground by a looming deadline.

According to legislators, passing a bill by Wednesday would leave enough time to override a gubernatorial veto during the legislative session, should the need arise. The House Democratic caucus issued a letter to the governor Wednesday night requesting he veto the map.

The Senate vote, 27-7, would be enough to override a gubernatorial veto. But the House tally, 96-55, would fall 13 votes short, even including the nine members who were absent for the vote.

A veto would give renewed hope to Rep. Russ Carnahan, D-St. Louis, who would lose his congressional district under the map approved by the Legislature. At the state Capitol on Wednesday, he emphasized that his camp is looking to a long road yet ahead.

"We're going to stay firm on getting to a map that respects the key regions of the state and especially that respects the St. Louis region in a way that doesn't slice and dice districts," Carnahan said in an interview.

The map could be redrawn if it faces a legal challenge. Wednesday, House Speaker Steve Tilley, R-Perryville, voiced confidence in the map's constitutionality.

"I do believe it will withstand legal challenge, and I'm going to encourage the governor next time I visit with him that he should look at the map and look how it's drawn, and encourage him to sign it," Tilley said.

The "Grand Compromise" map, as some legislators have termed it, moves the 2nd District north from its position on the original House map. The district would include more of St. Charles County and less of Jefferson County than the House originally wanted.

That could make for a more competitive 2nd District, currently the only new congressional district in which the incumbent member of Congress might not seek re-election. Tuesday, former Missouri Republican Party Chairwoman Ann Wagner announced the formation of an exploratory committee to look at running for the seat next year, in the likely event that current Rep. Todd Akin, R-Town and Country, runs for the Senate.

The map met the demands of state Sen. Jason Crowell, R-Cape Girardeau, who threatened to block any map in the Senate that included too much of Jefferson County in the rural 8th District. The compromise would include about 60,500 Jefferson County residents in the 8th.

With the approval of the Legislature, the map awaits action by the governor. Nixon's office has not yet indicated whether he will veto the proposal.