The SEIU ad features a group of people removing a bent American flagpole and raising a repaired one.

"Today, our immigration system is broken. Now Alaska's delegation is working to fix it, in a new way that reflects Alaska values," a narrator says in the ad.

It closes with a prompt for viewers to call Sens. Begich, Lisa MurkowskiLisa Ann MurkowskiSenators press administration on mental health parity Overnight Energy: Watchdogs unveil findings on EPA, Interior controversies | GAO says EPA violated law with soundproof booth | IG says Zinke could have avoided charter flight | GOP chair probes Pruitt's four email addresses GOP fractures over push to protect Russia probe MORE (R) and Rep. Don YoungDonald (Don) Edwin YoungPension committee must deliver on retirement promise Our leaders must end the hate before they burn America down Alaska rep denies suggesting armed Jews could have prevented Holocaust MORE (R) and thank them for their support for immigration reform.

The three recently signed a joint letter calling for an immigration bill to be brought up for consideration before the end of this session.

"Inspired by the words of our First Alaskans, and deeply committed to an inclusive state and nation, we join today to express our hope that the bipartisan comprehensive immigration reform bill being drafted by our colleague be brought to the floor of our respective bodies for consideration this session," the letter reads.

But NumbersUSA, a group trying to limit immigration to the U.S., launched an ad last week attacking Begich for expressing support for a reform proposal that includes both a pathway to citizenship and more visas for foreign workers. Begich is one of the most vulnerable incumbents in the nation, going into reelection in a state that voted for GOP presidential nominee Mitt Romney by nearly 15 percentage points.

The SEIU ad will run for a week in the Anchorage market, and is backed by a low five-figure buy.

Watch the ad: