WINSTON-SALEM, N.C. — Sen. Kay Hagan (D-N.C.) says that her Republican challenger in the November election, North Carolina House Speaker Thom Tillis, will be a tough challenger in her re-election bid.

“The stakes are high this year,” Hagan said to a crowd of about 300 Democrats gathered last month at Forsyth Technical Community College in Winston-Salem.

“My opponent, Speaker Tillis, and his special interest friends have already poured more than $12 million into our state, into this race against me,” Hagan said. “Thom Tillis and his friends are trying to buy this election.”

“They are not part of any community in North Carolina,” she added. “And they don’t care about our values. I want you to help me tell them that our state is not for sale.”

Hagan’s attack on Tillis is the latest salvo in her battle to keep the seat. Jordan Shaw, Tillis’ campaign spokesman, didn’t return repeated requests for comment.

However, Todd Poole, a spokesman for the N.C. Republican Party, criticized Hagan for her comments about Tillis’ campaign.

“Kay Hagan is a hypocrite who practices an absurdly blatant double standard when it comes to third-party spending,” Poole said. “Hagan loves to decry outside groups critiquing her liberal record and pointing out she has voted with President Obama 95 percent of the time during her career.”

“But Hagan has no problem with her liberal allies spending millions in North Carolina to save her failing campaign,” Poole said.

Political observers say that Hagan is vulnerable to Tillis’ candidacy because of her support of the Affordable Care Act, popularly known as Obamacare. And the Republicans in the Tar Heel State have won the past two general elections.

State Rep. Paul Luebke is a Durham County Democrat and a sociologist who has written two books on North Carolina politics. Luebke said he expects a close race between Hagan and Tillis in Hagan’s re-election bid.

Some voters are unhappy about the conservative legislation passed last year by the Republican-dominated state legislature, Luebke said.

“There is a widespread feeling that Republicans overreached on a number of issues,” Luebke said. “(Republican legislators) had a lack of commitment to education by ignoring teachers’ concerns, including their salaries. That has led to lot a dissatisfaction. Tillis is tied to the extreme policies of the Republican Party.”

Tillis and his Republican supporters will try to tie Hagan to her support of Obamacare, Luebke said.

“Tillis’ campaign will tag her as an ally of Obama’s botched program,” Luebke said.

But Hagan has portrayed herself as a moderate on issues important to North Carolinians, Luebke said. Her stance appeals to moderates, traditional Democrats and unaffiliated voters.

Luebke said he also expects the contest between Hagan and Tillis to be financially costly.

“It will be an outrageously expensive race,” Luebke said. “North Carolina is a large state with 10 million people. Each side will try to reach voters in lot of the state’s media markets.”

Washington Republicans hope that Hagan’s defeat will hand them a Senate majority this fall.

In 2012, Republican presidential candidate Mitt Romney beat Democratic President Barack Obama in North Carolina while Republican Pat McCrory, a former mayor of Charlotte, won the governor’s race in the state. In 2010, Republicans won a majority of seats in the N.C. General Assembly. The N.C. GOP maintained that majority in the 2012 election.

Pundits and political operatives say North Carolina, once a red state whose majority of voters helped elect Republicans such as Ronald Reagan, George H.W. Bush and his son, George W. Bush, to the presidency, became a purple state when Obama narrowly defeated Republican Sen. John McCain of Arizona in 2008.

Six years ago, Obama’s coattails helped Hagan defeat Republican Sen. Elizabeth Dole in her re-election bid. In 2014, Obama’s name is not on any ballots in North Carolina, and Hagan and the N.C. Democratic Party will run a campaign on her record as the state’s second female senator in Washington.

During the May 6 primary, Hagan and Tillis easily won their party’s nominations to run for the Senate seat in the fall election.

Hagan won 77 percent of the vote in the Democratic Party’s primary to beat two lesser-known Democratic candidates, according to state election results. In the Republican primary, Tillis won nearly 46 percent of the vote to avoid a runoff against seven other Republican candidates.

His primary opponents included tea-party backed candidates Dr. Greg Brannon of Cary, N.C., and the Rev. Mark Harris of Charlotte.

Hagan and Tillis will be joined by a third candidate on the November ballot. Libertarian Sean Haugh of Durham, N.C., won slightly more than 60 percent of the ballots from registered Libertarian voters in that party’s primary.

The number of registered voters in the state suggests that Hagan might have an advantage over Tillis on Nov. 4. Out of a total of 6.57 million registered voters in the North Carolina, 2.75 million are registered Democrats, 1.99 million are registered Republicans and 1.74 million are unaffiliated voters.