The National Republican Senatorial Committee is touting an expanding Senate map as the primary season concludes, arguing they're in strong position to win Senate control.

"Last summer, our friends at the [Democratic Senatorial Campaign Committee] wrote that divisive primaries and a failure to "expand the map" would leave only a half dozen competitive states to determine the Senate majority," NRSC Executive Director Rob Collins writes in a memo. "What a difference a year can make. Today, Republicans are in a strong position to win the Senate majority and we are proud of the candidates who are running."

The memo argues there are "at least fifteen Democratic held seats" that are in play to give them the six they need for a Senate majority. Collins names states like Iowa, Michigan, Colorado and New Hampshire, following Republican recruiting successes there.

"We've said that we have one goal: win the Majority. Our path has always been dependent on our ability to recruit and support candidates who fit their states and can win a general election," Collins continues.

Republicans have been mostly successful in boxing out fatally flawed primary candidates who would have otherwise buried their chances in swing states, and their prospects of taking the Senate look better now than they did a year ago.

Democrats have argued many of the candidates the establishment has gotten behind are too conservative to win, however. One glaring exception to the run of successes that Collins fails to mention is in Mississippi, where Sen. Thad CochranWilliam (Thad) Thad CochranWhite House requests B for missile defense to counter North Korea Senate narrowly passes 2018 budget, paving way for tax reform Live coverage: The Senate's 2018 budget 'vote-a-rama' MORE (R-Miss.) was forced into a primary runoff that many strategists expect he'll lose, and where Democrats are hopeful they can compete if Republicans nominate state Sen. Chris McDaniel (R).