GOP Primaries Wind Down, Obama Campaigning Heats Up

April will be a time of transition in politics. Republicans are winding down their presidential primary process, President Obama continues rolling out his re-election campaign and lawmakers are turning from the work of grinding out legislation to getting busy defending their seats.

Republican frontrunner Mitt Romney has his best chance yet to lock up his party's presidential nomination with a string of primaries in states where voters should be receptive to his call for party unity in order to focus on the well-funded Obama campaign.

On April 3, Romney is counting on strong showings in Maryland and the District of Columbia, but the big test for the former Massachusetts governor and rivals Rick Santorum and Newt Gingrich comes in Wisconsin. The Badger State is not just expected to be a swing state in the fall, but has been the site of some of the fiercest clashes between conservative Republicans swept into office in 2010 and powerful government-worker unions.

All the candidates, including Texas Rep. Ron Paul, have taken up the cause of embattled Gov. Scott Walker, who is facing a recall election backed by government unions outraged over his move to limit their collective bargaining power.

A big win in Wisconsin for Romney, who has the backing of home-state favorite, Paul Ryan, chairman of the House Budget Committee, could intensify calls from national party leaders for Santorum and Gingrich to drop their bids. Neither the former Pennsylvania senator nor the former House speaker are in position to win the nomination outright and are asking for voters' help in blocking Romney from a victory and forcing a contested Republican National Convention in August.

But if Santorum were to win, it could add power to his argument that Romney is undeserving of the nomination, and do so in time to set up a titanic struggle two weeks later in Santorum's former home state of Pennsylvania.

On April 24, Romney is expected to widen his already large delegate lead with victories in primaries being held in New York, Rhode Island, Connecticut and Delaware. But delegate-rich Pennsylvania could be Santorum's last stand. He represented the Keystone State in Congress for 16 years and has been banking on the state's Republicans to give his campaign a lift.

But the polls have tightened in Pennsylvania as Romney picks up momentum nationally and voters are reminded of the old wounds from Santorum's 2004 endorsement of then-Sen. Arlen Specter, a liberal Republican who would later switch parties and cast a deciding vote for President Obama's health law.

If he is beaten in his former home state, Santorum would face serious difficulties in keeping alive his bid to deny Romney the nomination ahead of the convention. A Romney win in Pennsylvania might be the knockout punch his campaign has been looking for.

Meanwhile, President Obama will continue to ramp up his re-election campaign. Having already started hitting harder at Romney in March, expect the Obama campaign to intensify its anti-Romney barrage as the likely Republican nominee emerges from the primary process.

Obama formally announced his re-election bid one year ago this month, but his activities have so far been mostly limited to lots of fundraising, the building of a massive campaign infrastructure and keeping up a steady pace of swing-state campaign visits.

Look for Obama to step up his effort in April as he begins putting all of the money and infrastructure to use in an effort to define Romney as an enemy of working-class Americans.

A similar escalation will come in the battles for the Senate and House.

Lawmakers have mopped up most of the necessary legislative work for the next few months and will be largely out of session during April. That means more time to raise funds and campaign in their home districts.

For some, the battles will be more urgent as they face tough primary tests. In Pennsylvania, redistricting has brought a clash between Democratic Reps. Jason Altmire and Mark Critz in the southwestern part of the state. The two incumbents have been clashing ahead of the April 24 primary and the fight is expected to intensify.