Both Comedy Central shows are up big time since returning on Jan. 7.

Both are posting their biggest audiences among adults 18-34 and 18-49 since at least September and both are well up from this time last year.

“Daily Show with Jon Stewart” so far this month is averaging 358,000 viewers in the 18-34 demographic, up 17 percent from the same time period in 2007. It’s up 9 percent among 18-49s, to 535,000 viewers.

“The Colbert Report” is up 21 percent in 18-34s, to 329,000, and 15 percent in 18-49s, to 507,000 viewers, compared to a year ago.

By contrast, the late-night broadcast shows are suffering. “Tonight,” while still No. 1, is down 25 percent from last year in 18-49s. NBC’s “Late Night with Conan O’Brien” is down 18 percent. Both also returned without their writers. CBS’s “Letterman” is flat to last year, while ABC’s “Jimmy Kimmel” is down 14 percent. Ferguson is down 14 percent.

"Daily” and "Colbert" have a few things in their favor that the late-night broadcast shows don’t, and one is the presidential primaries and candidates, who are in the news each day. Both shows are heavily political, and these are the best of times for their humor.

“When these shows weren’t on, it wasn’t the gags you were missing. It was about missing being part of the national dialogue,” says Stephen Battaglio, senior correspondent at TV Guide. “The ‘Daily Show’ is in a pretty good groove. The same goes with Colbert. He’s extraordinary, almost like a performance artist. He can riff.”

Also, the broadcast shows rely heavily on celebrity guests, and those are in shorter supply with the writers' strike now in its third month and many actors refusing to go on the air in support of writers. That's hurt them considerably.

Stewart and Colbert rely more on their own personalities and humor.

But “Daily” and “Colbert” also have a loyal following of young viewers, notes Brad Adgate, senior vice president of corporate research at Horizon Media.

“With everything going on with the primaries and caucuses, this is the only type of place you can get satire about all this,” he says. “They have a loyal audience, who are young, and this is one of their sources for the news.”

Still, “Daily” and “Colbert” got off to a wobbly start after their return, with both finding their pacing and humor without writers only after a few uneven episodes.

“Daily” is doing a lot less filming outside the studio than it used to, and in support of the writers it’s temporarily changed its name from “The Daily Show” to “A Daily Show.”

And that raises what could be a big issue: How long can they keep up the pace? Even the funniest of funnymen wear down in time, and in time the strain will begin to show.