The end of the first fundraising quarter also marked the end of the calm before the storm of spending in the 2012 fight for control of the Senate.

Millions will be doled out over the next seven months, most of it on TV ads and other pricey forms of voter persuasion. So far, outside group spending has yet to kick into high gear, and head-to-head polls in individual races haven’t moved much. But Senate races in states such as Missouri and Montana have already seen third-party ad offensives, and the campaign committees are beginning to tip their hand on TV spending strategies.

“There will come a moment in the summer or early fall when people begin to pay attention,” said Jonathan Collegio, spokesman for the GOP-aligned American Crossroads, which will likely spend one-third of its potential $300 million budget on House and Senate races.

There is no doubt Democrats feel better than they did six months ago about holding the majority, and Republicans continue to see multiple paths to the finish line. Some races are still shaking out, with another new Republican candidate possibly emerging in Florida and primaries in other crucial states still unfolding. But tossup races in states such as Montana and Virginia, where the players have been known for a year now, are still within the margin of error.

That will all reach a tipping point once nominations are won, voters tune in and campaigns and outside groups gear up for an onslaught of spending at the presidential and Congressional levels.

“It’s not the calm before a sea-change storm, but it is a calm before all the money,” Democratic media strategist Steve Murphy said.

It’s too early to tell exactly where the majority will be won or lost, but the field has mostly solidified into a dozen or so competitive seats out of 33 this cycle. Senate control might ultimately rest on a handful of swing states such as New Mexico, Virginia and Wisconsin, should Republicans close the deal on four open Democratic seats in GOP-leaning states and Democrats pick up a couple of Republican seats — none of which is a given.

Republicans would need to net four Democratic seats to win the majority if President Barack Obama wins re-election, one fewer if Mitt Romney claims the White House.

Outside money has already begun flowing into some of these states in the form of independent expenditures and issue advocacy ads. According to Federal Election Commission IE records, most of the IE spending has come in races with competitive Republican primaries, including Indiana, Nebraska, Texas and Utah.

“Republicans are going to have access to more money than Democrats,” Murphy said of outside groups. “As long as the Democrats are competitive financially, a lot of this super PAC money is just going to be bombing the rubble.”

The National Republican Senatorial Committee signaled last week where it intends to spend its valuable resources, reserving $25 million in airtime in six top battlegrounds. In its initial wave of reservations, the committee is targeting Sens. Jon Tester (Mont.) and Claire McCaskill (Mo.) and the open Democratic seats in Nebraska, Virginia and Wisconsin. It’s also assisting Sen. Dean Heller (Nev.), who is in a tossup race in a top presidential battleground.

The Democratic Senatorial Campaign Committee has not yet indicated where it will spend, but both committees will likely be targeting most of the same states and will no doubt move money around as November approaches.

Additional states where outside money could end up are Arizona, Hawaii, Indiana, North Dakota and Ohio. Florida is prohibitively expensive, making Sen. Bill Nelson’s (D) $9.5 million in cash on hand at the end of March an even greater advantage in that competitive state. Ohio will also be pricey, given its competitiveness at the presidential level.

“There will be enormous political clutter in the key presidential battleground states,” Republican media strategist Erik Potholm said. “So campaigns will look at a variety of media strategies and tactics to try to get their messages out, including going up earlier to try to define their races.”

McCaskill, who is likely the most vulnerable incumbent in the country, still has no idea who her opponent will be. Running as an independent Democrat against a generic Republican in a state the Obama campaign isn’t targeting, McCaskill used her first TV ad in February to run against the outside groups already spending against her.

Based on the vulnerability of the incumbent and the relatively reasonable cost of running ads, Missouri is a top candidate for outside spending. McCaskill is getting air support as well from outside groups. Patriot Majority USA reported an IE of just more than $200,000 on April 13, according to FEC records.

Collegio, of American Crossroads, said New Mexico could be the sleeper race of the cycle and noted Ohio and Wisconsin as other top pickup opportunities for Republicans outside of the ones getting the most press.

While polling has been generally stagnant in most races, Democrats say the needle is indeed moving in their direction.

“It’s proving to be a favorable political climate for Democrats, increasing the chances that Democrats will hold the majority in the Senate,” said J.B. Poersch, a media strategist and former DSCC executive director.

The Democratic Congressional Campaign Committee leaked this week where it’s placing $32 million worth of its first TV reservations. The DSCC and National Republican Congressional Committee, which are working to hold their majorities, might also soon follow suit.

“The most important reason to place early is to save money and get the best inventory,” Potholm said. “But another strategic benefit of reserving time early is that it signals very clearly to your friends and allies in outside groups where they should fill in the calendar with their media placement.”