(AP Photo/John Minchillo)

The campaigns of Hillary Clinton and Bernie Sanders have agreed on a rough schedule for four new debates over the next few months, according to various sources, a move that shows the Democratic primary is now set to shift into a higher gear and signals we may be headed for a long, drawn-out battle.

The four debates will be sanctioned by the Democratic National Committee, a spokesman for the DNC, Luis Miranda, confirms to me. “They will all be sanctioned,” Miranda says.

The first of these will be tomorrow night in New Hampshire, to air on MSNBC. The second will be in Flint, Michigan (as Hillary Clinton has requested) in March; the third will be in Pennsylvania in April, and the fourth will be in California in May, a source close to the talks confirms.

On CNN just now, Bernie Sanders was asked by CNN’s Wolf Blitzer whether the two campaigns had agreed on upcoming debates. Blitzer noted that Sanders confirmed earlier today that he would be attending tomorrow’s MSNBC debate, and asked Sanders whether the Clinton camp had agreed to the three more debates he had wanted in exchange for agreeing to tomorrow’s affair:

BLITZER: You now say you will be participating in that Democratic presidential debate tomorrow night. Did you get the commitments from Secretary Clinton you wanted about three additional Democratic presidential debates down the road?

SANDERS: Yes. To the best of my knowledge we have. We didn’t get all the commitments that I wanted. We got California, we got Michigan — and that’s good. I wanted a debate in New York City….but Secretary Clinton has not agreed to do that. But I believe we’re looking at a debate in Pennsylvania…but I do believe we have her commitment, as I understand it, for three additional debates.

As noted above, DNC spokesman Miranda confirms that they will be sanctioned, and a source close to the talks confirms the months and locations. While there are still some last minute scheduling details to figure out — and while one supposes it’s always possible that something could go wrong — it looks like the debates are set to happen, and the final details are being worked out in negotiations being facilitated by the DNC.

This is pretty significant, because the previously announced schedule would have meant there were only two more debates happening. That had become increasingly untenable, now that we’re looking at serious, competitive, protracted primary, and instead, we may now get six more debates. And remember, now that Martin O’Malley has dropped out, these will be head-to-head affairs. All this will mean more exposure to a national audience for the Democratic candidates and their ideas, perhaps contrasting well with the intensifying GOP primary madness, and it will hopefully put to rest the criticism of the previous debate schedule and allay the sense that it was compromising the integrity of the primary process and wasn’t serving the party well.