In Colorado, where a tough battle is underway for this fall's U.S. Senate election, Democrat Mark Udall is accusing his opponent Cory Gardner of having a radical agenda on abortion and birth control, and so far in the campaign he's also emphasized gay rights, immigration and other divisive social issues.

Republicans have taken note of the strategy. "Udall is running his entire campaign on social issues," Brad Dayspring, a strategist with the National Republican Senatorial Committee, told the New York Times earlier this week. "All they talk about is birth control, 'personhood,' abortion."

New York Times writer John Harwood predicted many other Democrats will join Udall in talking up those issues in advance of November's midterm elections. Democrats are at risk of losing control of the Senate, which makes races like the one in Colorado critical to the party's overall fortunes.

Kentucky is another attention-grabbing race, where 35-year-old Democrat Alison Lundergan Grimes is trying to unseat the Senate's minority leader, Mitch McConnell, 72. In a blistering speech on Aug. 2, she said if he were a TV show, McConnell would be Mad Men because of his unfair treatment of women and because he's "stuck in 1968." He doesn't believe women deserve equal pay for equal work, she said in her attack on the longtime senator, who was seated a few feet away.

That Udall and other Democratic candidates are highlighting divisive social issues shows that the politics of those issues is shifting, Harwood noted in the New York Times piece. Whereas Republicans for decades were able to use certain issues as political ammunition and to rally voters around them, the wedge issues are now cutting the other way, for Democrats.

American demographics have changed and along with them, attitudes on social issues including same-sex marriage, contraception and marijuana, which means Democrats and Republicans have been forced to re-evaluate their election strategies. How much or how little should they emphasize social issues in their appeals to voters?

'The country is shifting'

The answer depends on where the race is and who is running, according to Justin Barasky, national press secretary for the Democratic Senatorial Campaign Committee.

In Colorado, Republican candidate Gardner's support for measures to restrict access to birth control is a "huge liability," Barasky said in an interview.

"It's not surprising to me that the [Republican senatorial committee] is upset that we're talking about it there," he said.

U.S. Senator Mark Udall, seen speaking during a 2012 memorial service in Arizona, is running for re-election in Colorado and has accused his opponent Cory Gardner of having a radical agenda on birth control and abortion. (Laura Segall/Reuters) If Democrats seem to be talking more about social issues in this election cycle compared to previous ones, it's not just because of changing attitudes but because of who they are up against, Barasky suggested.

"I think the country is shifting, but it is also much more of a reflection of the fact that the Republican Party is shifting and it's shifting away from where the rest of the country is," he said.

Abortion and contraception, for example, didn't feature as prominently the last time around, Barasky said, because there weren't as many Republican candidates supporting the "personhood" movement — which seeks to give rights to a fertilized human egg.

"This cycle they're all pro-personhood," he said. "It's a much more conservative, right-wing, extreme slate of Senate candidates than we've ever seen."

Gardner in Colorado actually backed away from his past support of personhood once he entered the Senate race, but Udall isn't dropping the issue and has already released two television attack ads related to it.

The ongoing debate about contraception and abortion was given new life a few weeks ago when the Supreme Court ruled that the company Hobby Lobby Stores Inc. could opt out of health insurance coverage of some birth control for its employees because of religious objections.

The ruling provided an opportunity for Democrats and Republicans to define themselves on the issue and Democrats used it to boast that they are the ones who care more about women and women's issues.

Female, young voters sought after

In recent elections, Democrats have fared better with women than Republicans, and Dan Hopkins, a political scientist at Georgetown University, said in an interview that Democratic strategists are using social issues to broadly appeal both to women and young voters.

"I think the Democrats are trying to find ways to say to the female voters, to young voters, ‘We are the party that shares your values,' " he said. "Given the particular strategic choices that these candidates face, social issues are often productive for them as a way to say to a group of voters, 'You're more on my side than on my opponent's side.' "

Same-sex marriage laws, for example, have been changing through the courts and at the state levels, yet candidates running for Senate seats might still use the issue of gay rights as a symbolic one.

"Candidates will use those kinds of issues as symbols of affinity," Hopkins said.

Some Republicans say their party isn't interested in making same-sex marriage a campaign issue and it's the Democrats who are trying to stir controversy.

"I'm not saying it's not important," Wisconsin Gov. Scott Walker, who is up for re-election, told The Associated Press. "But Republicans haven't been talking about this. We've been talking about economic and fiscal issues. It's those on the left that are pushing it."

The economy, while it's improving, is an issue the Democrats are likely not ready to tether themselves to in an election, Hopkins explained, which could be another reason for the emphasis on social issues. Add to that the fact that foreign policy isn't at the forefront of voters' minds the way it was when thousands of Americans were fighting in Iraq and Afghanistan.

Democrats are exuding confidence that they are on the right side of the social issues and they're trying to portray Republicans as out of touch with Americans' attitudes, especially when it comes to women.

"I do think that the Republican Party is struggling to keep pace with the times," said Barasky, the Democratic Senatorial Campaign Committee spokesman.

Democrats' greater popularity with women works in their favour, but the party doesn't necessarily have to do much to take advantage of that, he said, because Republicans are essentially shooting themselves in the foot.

"Whether it's equal pay, or access to birth control, there are Republican Senate candidates across the map — whether we're in a blue state or a red state — that are hostile to women's issues. And that certainly, without a doubt, helps Democrats."