The decision by Rep. Gabrielle Giffords (D-Ariz.) to resign from Congress means a special election will be held for her seat — a race that could well be quite competitive.

View Photo Gallery: Rep. Gabrielle Giffords, who has been undergoing physical and speech therapy for the past year, says she will resign from Congress this week.

According to state law, Gov. Jan Brewer (R-Ariz.) must set a date for a special election primary 80 to 90 days after Giffords formally steps down, and a general election will be set for 50 to 60 days after the primary. So the primary election for Giffords seat will likely be held in late April with the general election in June.

The state’s independent redistricting comission made Giffords’ swing seat slightly more Democratic. But that map is under dispute, and a special election for Giffords’ seat will be held under the old lines.

That’s the map under which Giffords was reelected in 2010 by a mere 1.3 percent margin. Her district voted for Sen. John McCain (R-Ariz.) in 2008.

But the special circumstances — Giffords has become a national hero since the assassination attempt against her last January — surrounding the seat could give Democrats something of a boost.

“The entire nation has felt like one of Gabrielle Giffords’ constituents,” Democratic Congressional Campaign Committee Chairman Steve Israel (D-N.Y.) said in a statement. “We look forward to working with a Democratic candidate who fits this district and shares those values that Gabrielle holds dear to carry on her work.”

Democrats say it’s too early to talk about a replacement for Giffords in the House, but that candidates will emerge soon.

A Democratic source in the state said the party has a “deep bench” and is confident about competing in both the special election and next fall.

Giffords’ husband, retired astronaut Mark Kelly, has already said he’s not interested in running for Congress.

On the Republican side, state Sen. Frank Antenori expressed interest in the seat back in August.

The fields on both sides are likely to grow as aspiring pols jumpt at the chance for an open seat.