CASPER, Wyo. — Senator Obama sought to regain lost momentum in Wyoming’s caucuses days after Senator Clinton’s nearly clean sweep of major primaries in their tight Democratic presidential race.

Twelve national convention delegates are at stake today in caucuses around the state, a small but critical prize in the close race for the party’s nod. The epic battle between Mrs. Clinton and Mr. Obama has given the state’s Democrats — outnumbered more than 2-to-1 by Republicans — a relevancy they haven’t experienced in a presidential race in nearly 50 years.

Mrs. Clinton won victories Tuesday in primaries in Texas, Ohio, and Rhode Island, reviving her candidacy. But Mr. Obama has prevailed in 12 of the 15 caucuses, which rely on greater campaign organization and voter commitment than primaries. A winner has not been declared in Texas’s caucuses; the state held both last Tuesday.

“Wyoming is usually not thought of as a momentum state, but it happens to fall on a calendar at a good time for both of them,” a political science chair at the University of Colorado who is an expert in Western politics, Kenneth Bickers, said. “Both of them need to be able to claim a victory. Both of them need whatever delegates they can get to help move their delegate count in a positive direction.”

About 59,000 registered Democrats are eligible to participate in Wyoming’s 23 county caucuses.

A victory in Wyoming would boost the winner going into this Tuesday’s primary in Mississippi, where Mr. Obama is again favored because of the state’s significant black population.

Only in the last few weeks have the campaigns stepped up their presence in Wyoming, opening offices and calling voters and sending mailers. The first visit came Thursday, when President Clinton made three appearances in Wyoming.

The candidates followed yesterday. Mrs. Clinton held town-hall meetings in Casper and Cheyenne. Mr. Obama held a town hall in Casper and a rally in Laramie at the University of Wyoming, counting on support from college students. Mr. Obama has been running television and radio ads in the state, while Mrs. Clinton has been running radio ads.

The state’s top Democrat — Governor Freudenthal — has declined to endorse either candidate, saying they haven’t talked enough about Western issues. The state party chair, John Millin, is backing Mr. Obama, while a former governor, Mike Sullivan, has endorsed Mrs. Clinton.

Mr. Obama holds the lead in delegates, 1,571-1,462, but Mrs. Clinton has the edge with superdelegates — the party officials and elected leaders — 242-210. A total of 2,025 delegates is needed to win the nomination.

Although a win in Wyoming may not persuade many superdelegates, it will be one more prize for the candidates as they make their case for the nomination.

“Both of them will make the point that it’s a trend for them if they win (Wyoming),” Mr. Bickers said.

Wyoming Democrats have relished the attention, harkening back to the 1960 Democratic National Convention when the state’s delegation cast 15 votes that pushed Sen. John F. Kennedy over the top for the nomination.

A party spokesman, Bill Luckett, said he’s never seen Wyoming Democrats in such a frenzy.

“People are really excited about this year and the role Wyoming is playing,” Mr. Luckett said.