Why are Democrats suddenly cheering in Ohio?

Ted Strickland, a Democrat and former Ohio governor, announced Wednesday he's taking on GOP Sen. Rob Portman. That will be a marquee Senate race in a cycle with lots of opportunities for Democrats.

Ohio is always big in presidential races. It’s the ultimate bellwether state. Now add Ohio to the column called “marquee Senate races of 2016.”

Ted Strickland, the state’s Democratic former governor, announced Wednesday that he’s running against Republican Sen. Rob Portman, a big score for the party out of power on Capitol Hill. Democrats need a net gain of five seats to retake control of the Senate, in a cycle whose map favors the Democrats.

Republicans are defending 24 seats in 2016, versus only 10 for the Democrats. Of those, 10 Republican-held seats are competitive, while two Democrat-held seats are, according to the Rothenberg & Gonzales Political Report.

Democrats are also better at turning out their “base” – minorities, single women, and young voters – in presidential election years.

Mr. Strickland is a Democratic elder statesman, with a strong statewide profile. He lost reelection to current Gov. John Kasich (R) in 2010, a tough year for Democrats, by two percentage points. Senator Portman, respected in Washington as a leader of the center-right, isn’t so popular at home. Only 37 percent of Ohioans gave him positive job marks in a recent Quinnipiac poll.

Strickland is the second Democrat to enter the race to take on Portman, a sign of the incumbent’s vulnerability. Cincinnati Councilman P.G. Sittenfeld announced in January and has raised $500,000 so far, according to The Columbus Dispatch.

Though it’s only February 2015, Democrats are moving fast to fill slots in the 2016 Senate cycle. Here’s a rundown:

California. California Attorney General Kamala Harris (D) declared for the Senate within days of Democratic Sen. Barbara Boxer’s announcement Jan. 8 that she’s not running for reelection. On Tuesday, former Los Angeles Mayor Antonio Villaraigosa announced he won’t run, leaving Ms. Harris as the early front-runner to replace Senator Boxer in solid-blue California.

A Field Poll of likely California voters released Feb. 18 shows former Secretary of State Condoleezza Rice coming out on top, three percentage points ahead of Harris, but Ms. Rice says she won’t run.

New Hampshire. Sen. Kelly Ayotte (R) is seen as vulnerable in this presidential tossup state, and Gov. Maggie Hassan (D) would be her party’s top “get” if she agrees to run. An NBC News/Marist poll released Feb. 17 shows Governor Hassan beating Senator Ayotte 48 percent to 44 percent.

Pennsylvania. Sen. Patrick Toomey (R) is another vulnerable incumbent in a state that leans Democratic in presidential contests. Former Rep. Joe Sestak (D) hasn’t formally jumped into the race yet, but he never really stopped running after losing narrowly to Senator Toomey in 2010.

Illinois. Sen. Mark Kirk (R) has health and political problems, leaving him vulnerable to a challenge in solidly Democratic Illinois. In January, second-term Rep. Tammy Duckworth (D) said she was taking a “real serious look” at the race, but is just now getting back to work after having a baby in November.

Florida. Sen. Marco Rubio (R) says he’ll either run for president or run for reelection to the Senate. Either way, more than one Democrat is looking at getting into the Senate. And even if Senator Rubio defers his presidential ambitions, his grip on his Senate seat in battleground Florida isn’t solid. One familiar face looking at Rubio’s seat is Democratic National Committee chair Debbie Wasserman Schultz, who also represents Florida’s 23rd Congressional District.

Another Democrat who could be strong statewide is Rep. Patrick Murphy. He won reelection big last November in his conservative Florida district.

Wisconsin. Sen. Ron Johnson (R) won his first term in 2010, the first tea party-fueled cycle. Now, Democratic-leaning Wisconsin could have a rematch of that race, if ex-Sen. Russ Feingold (D) gets in as expected. In a speech Tuesday at the US Institute of Peace, Mr. Feingold dropped a hint that he was headed in that direction, thanking his “once, current, and, I hope, future Chief of Staff Mary Irvine.”

Since 2013, Feingold has served as a special State Department envoy to the Great Lakes Region of Africa and the Democratic Republic of the Congo. He resigned last week.

North Carolina. Sen. Richard Burr (R) could face a tough challenger in ex-Sen. Kay Hagan (D), who won kudos last year for running a strong (though losing) reelection campaign in a bad year for Democrats. Ms. Hagan is especially good at raising money, and she is national Democrats’ first choice to take on Senator Burr. North Carolina was once solid red, but Barack Obama won it in 2008. 

Nationwide, the two Democrats seen as vulnerable are Senate minority leader Harry Reid of Nevada and Sen. Michael Bennet of Colorado.