By Lisa Mascaro, Tribune Washington Bureau for the LA Times

With this fall’s midterm elections, the number of women serving in Congress could drop for the first time in a generation — a twist on a political season many had dubbed “the year of the woman.”

If large numbers of Democratic incumbents lose in November, as expected, many women could be replaced by men. Female candidates tend to do better in Democratic years, and 2010 is shaping up as a successful year for Republicans.

Women now hold 90 seats in Congress: 69 are Democrats and 21 are Republicans. After the November election, Congress could end up with as many as 10 fewer female members, prognosticators now say, the first backslide in the uninterrupted march of women to Washington since 1978.

The prospect of a setback has advocates of women’s rights in disbelief, but determined to try to prevent it. “That is not going to happen,” said Terry O’Neill, president of the National Organization for Women, which is working to elect candidates of both sexes who support women’s equality.

While political attention has focused this year on Sarah Palin‘s handpicked candidates and on a record number of Republican women running for House seats, primary losses have thinned their ranks to several dozen.

In fact, just four women are among the GOP’s 46 “Young Guns,” as the party calls its frontline challengers who are considered future leaders.

Republican campaign officials expect more female candidates will join the group as they prove themselves with the fundraising and organization needed to mount serious campaigns. But the bulk of “Republican candidates in these really promising seats are men,” said David Wasserman, a congressional analyst at the Cook Political Report who has been monitoring the situation.

Many of the vulnerable Democratic women this fall first arrived on the waves of the 2006 and 2008 elections, but now face tough odds in districts that have since soured on the party in power and on President Obama’s agenda.

Freshman Rep. Debbie Halvorson (D-Ill.), who won in 2008 in an increasingly split district long dominated by the GOP, is being challenged by a 32-year-old Iraq war veteran, Adam Kinzinger, one of the Young Guns.

Another endangered Democratic congresswoman, Betsy Markey, a freshman from Colorado, is being challenged by a fifth-generation farmer and state representative, Cory Gardner, who is also a Young Gun.

Republican officials in Washington say that their female candidates will make gains, pointing to Montgomery City Councilwoman Martha Roby, who is running against Democratic Rep. Bobby Bright in Alabama, and ophthalmologist Nan Hayworth, who hopes to oust two-term Democratic Rep. John Hall in New York.

“The 2010 candidate recruitment class is a formidable one, and that includes a number of top-tier female candidates who will likely be called ‘congresswoman’ after November,” said Ken Spain, spokesman for the National Republican Campaign Committee.

In the Senate, if voters reject Democrats Blanche Lincoln of Arkansas and Patty Murray of Washington, both will probably be replaced by men.

Republican female candidates could pick up Senate seats in Connecticut, where World Wrestling Entertainment‘s Linda McMahon is running for the open seat held by retiring Sen. Christopher J. Dodd, and in Nevada, where “tea party” favorite Sharron Angle wants to oust Senate Majority Leader Harry Reid.

Yet overall, the numbers are not likely to overcome potential losses by women.

The fortunes of women in Congress have ebbed and flowed since the first, Jeannette Rankin, a Republican from Montana, took office in the House in 1917, three years before the 19th Amendment to the Constitution gave women the right to vote.

Women made mostly steady gains through the election of President Kennedy in 1960, when 20 women held office in Congress, according to the Center for American Women and Politics at Rutgers University.

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