Rising G.O.P. Star Expected to Challenge Arkansas Democrat

Representative Tom Cotton, Republican of Arkansas, is expected to announce his challenge to Senator Mark Pryor of Arkansas in 2014, according to two Republicans familiar with his thinking. For Mr. Pryor, a two-term Democrat, the bid would further complicate his efforts to hold onto his already vulnerable seat.

The Associated Press, which first reported Mr. Cotton’s plans, said he would announce his decision next Tuesday at an event in Dardanelle, Ark., his hometown.

Mr. Cotton, a 36-year-old freshman lawmaker, was elected in 2012 and quickly became a rising star in his party, with his name buzzed about as a potential Senate candidate almost immediately. Supporters noted his résumé â€" a graduate of Harvard University and Harvard Law School; an Iraq and Afghanistan war veteran and a former McKinsey & Company management consultant â€" and his folksy drawl and ability to chat easily about his family’s cattle farm.

Though the Pryor name is dynastic in Arkansas â€" Mr. Pryor holds the Senate seat that was his father’s for nearly two decades â€" Mr. Pryor was already facing an uphill fight in his increasingly Republican home state. Mitt Romney won Arkansas with 60.5 percent of the vote in 2012, and voters there elected an entirely Republican slate of House members last year, as well.

The Rothenberg Political Report rated the Arkansas Senate race a “pure toss-up,” along with the open Senate seat in Montana and Senator Mary Landrieu’s seat in Louisiana.

Mr. Cotton’s office would not confirm reports that he is planning to run for Senate, but did say he plans to discuss his future plans generally next week in Arkansas.

“On Tuesday, Tom is inviting his hometown and all who have supported him along the way to hear about his fight to represent Arkansas’ values in D.C.,” said Caroline Rabbitt, Mr. Cotton’s communications director. “He looks forward to sharing his plans to continue that fight in the coming year.”

Mr. Pryor’s campaign did not wait for Mr. Cotton’s challenge to become official before going on the attack.

“In seven short months, Tom Cotton’s reckless and irresponsible voting record has alienated Arkansas farmers, seniors, students, women, parents and the business community by voting against such measures as the farm bill, student loans, the Violence Against Women Act, and trying to cut Social Security and Medicare,” Jeff Weaver, Mr. Pryor’s campaign manager, said in a statement. “Instead of putting Arkansas first, he has put his own political career ahead of the people of Arkansas and sided with Washington insiders and special interests. When the people of our state review Tom Cotton’s record, they won’t like what they see.”

However, American Crossroads, a conservative “super PAC,” was eager to see Mr. Cotton’s bid go forward.

“One of the weakest Democrats in the Senate this cycle is now facing potentially the strongest Republican challenger of the cycle,” Steven J. Law, the group’s president, said in an e-mail statement. “Representative Cotton is a conservative leader and rock star candidate. Arkansas is now one of the very top pickup opportunities for Republicans this cycle, and we are excited to get engaged in the race on behalf of Rep. Tom Cotton.”