Chris Wallace's relentlessness may have finally paid off. The "Fox News Sunday" host told me in April that he asks every week to interview Hillary Clinton. Until now, the answer has always been no. But Wallace just landed Clinton's first sit-down interview as the Democratic presidential nominee, according to Fox News. The conversation — a major coup for a cable channel Clinton generally avoids — will be taped Friday or Saturday and air Sunday.

Wallace announced the interview agreement on the air Wednesday afternoon.

"I've been working on it for 15 months, since she announced [her candidacy], and what I've learned is — I've always learned, we've all learned — the value of persistence," he said.

"As long as I've been trying to get the interview, I've had a file of questions I want to ask her," Wallace added. "I keep updating it. There's plenty to talk to her about. I've only had 15 months to prepare."

After freezing out Fox News for the first 11 months of her campaign, Clinton has been slowly warming to a network whose deep roster of conservative commentators makes it a favorite outlet for Republicans. She participated in a town hall event moderated by Bret Baier in March, granted an interview to Baier in June and called in to Bill O'Reilly's program this month.

By agreeing to the Wallace interview — and doing it before she talks to anyone else — Clinton is signaling louder than ever her intent to court Republican voters who are unhappy with their party's nominee.

"She is going to make a play for disenfranchised Republicans who are not buying into Donald Trump," Baier told me before the conventions. "It is in her interest to do those interviews."

Clinton will, of course, be making a play for the Democrats and independents in the Fox News audience, too, but poaching Never Trump conservatives is likely the primary goal here. It's a media strategy that could work. But the interview prep here will be critical — Wallace prides himself on being a tough interviewer, and he's had a long time to get ready for this one.