Washington (CNN) After multiple instances of gun violence -- such as the Parkland, Florida, high school mass shooting that left 17 dead -- some gun control advocates have called for a ban on AR-15-style guns, similar to one the US had in place until it expired in 2004.

But that ban, which would need an act of Congress to be revived, isn't likely to go anywhere on Capitol Hill anytime soon, most congressional observers say.

The alleged gunman Nikolas Cruz legally purchased the firearm he used in the shooting, an AR-15-style rifle, in the state of Florida nearly a year ago, according Peter J. Forcelli, special agent in charge of the Miami field division of the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The Colt AR-15, the style of gun on which the Parkland shooting weapon was based, was among those outlawed for 10 years under the 1994 law but is now legal.

Even under the ban, manufacturers of guns used loopholes to continue being able to produce guns very similar to the AR-15 by changing details on the weapon or changing its name. For example, the ban didn't cover versions of these weapons unless they had two of cosmetic features: a folding stock, a bayonet mount, a "conspicuously protruding" pistol grip, a flash suppressor or a grenade launcher.

In order to understand where the country is headed with gun control, it's important to know how we got here.

The 1994 assault weapons ban

In many of the mass shootings in the last several years, including the Las Vegas massacre on October 1 and the Texas church shooting on November 5, the gunmen used semi-automatic firearms.

But they weren't always legal to buy and sell.

In 1994, then-President Bill Clinton pushed an assault weapons ban through Congress, and it had bipartisan support.

Former presidents Ronald Reagan, Jimmy Carter and Gerald Ford even co-authored a letter to the House of Representatives expressing their support at the time.

"This is a matter of vital importance to the public safety," the letter read. "We urge you to listen to the American public and to the law enforcement community and support a ban on the further manufacture of these weapons."

Clinton's ban outlawed more than a dozen types of semi-automatic weapons similar to the rifle used in the Parkland shooting. There was a clause in the weapons ban that stated it would expire in 10 years unless Congress reauthorized it, which didn't happen.

Some Democrats wanted to renew the ban, but there weren't enough of them to make it happen. So the ban expired in 2004.

Divided calls over the ban

It's not just those on the left who have floated the idea of reviving the ban. A top Republican donor vowed over the weekend to stop cutting checks for candidates and political groups that do not support a ban on assault weapons.

"All I want to do is to restore sanity and adopt this assault weapon ban so that our children can get back in school and be safe and not get shot," real estate developer Al Hoffman Jr. told CNN's Ana Cabrera.

A majority of Americans blame Congress and President Donald Trump for not doing more to prevent mass shootings, according to a Washington Post/ABC News poll released on Tuesday

Among party lines, 86% of Democrats and 57% of independents said stricter gun control would have prevented the shooting, but only 29% of Republicans said the same thing.

In that poll, there was no rise in support for a ban on assault weapons compared to two years ago. In addition, 42% of respondents said the Florida shooting could have been prevented if school teachers were allowed to carry guns.

In a separate Quinnipiac poll released Tuesday, 66% of people surveyed support stricter gun laws in the US, including 86% of Democrats, 69% of independents -- but just 34% of Republicans. That's the highest since Quinnipiac began asking in November 2015.

And 67% of people surveyed support a nationwide ban on the sale of assault weapons. Out of that percentage, 43% of Republicans surveyed support it, as well as 91% of Democrats and 63% of independents.

Instead, the gun control debate in Congress appears to be heading toward updating the background check process in the US, if anything.

Other efforts to renew the ban have failed

One of the strongest advocates in Congress for a new assault weapons ban has been Sen. Dianne Feinstein, D-California, who reintroduced a bill the that would ban the sale of that kind of weapon after the deadly elementary school shooting in Newtown, Connecticut, that left 20 children and six adults dead in 2012.

Feinstein, who helped champion the 1994 legislation, created her proposal as an upgrade to the assault weapons ban that expired in 2004 -- and the legislation would have also outlawed ammunition magazines that hold more than 10 rounds.

When her proposal passed out of the Senate Judiciary Committee at the time, then-Senate Majority Leader Harry Reid decided not to include the proposed assault weapons ban in gun legislation going to the full Senate for consideration because including it would guarantee the measure would be blocked by a Republican filibuster.

Instead, she proposed the ban as an amendment to gun legislation on the Senate floor in order to get a vote on it.

In the end, the proposal failed on a Senate vote of 40 to 60.

What's happening now

In the past, the most serious efforts at bipartisan gun bills have dealt with background checks and not banning specific kinds of weapons, and that's likely to be the case this year where some key Democratic senators are running for re-election in states won last year by President Donald Trump.

Even this week, the White House said Monday Trump "is supportive of efforts to improve the federal background check system" for gun purchases and Tuesday the President said he has directed his attorney general to propose changes that would ban so-called bump stocks, which make it easier to fire rounds quicker.

Principal deputy press secretary Raj Shah said that Trump spoke with Sen. John Cornyn, a Texas Republican, on Friday about a bill he introduced with Sen. Chris Murphy, a Connecticut Democrat, that aims to strengthen how state and federal governments report offenses that could prohibit people from buying a gun.

While the House passed a bill that included this provision in December, a Senate bill with the same proposals has stalled. It's been referred to the Judiciary Committee, but it has not been taken up for a vote.

The House bill was merged with two measures that have bipartisan support, including the measure to fill in holes in the National Instant Criminal Background Check System. The measure, that does not have bipartisan support, would loosen gun regulations and allow those with permits for carrying concealed weapons to legally travel with those firearms to other states, which was a top priority of the National Rifle Association.

The Senate legislation wouldn't strengthen background checks, but ensure that federal and state authorities comply with existing law and require them to report criminal history records to the National Instant Criminal Background Check System.

It's unclear at this point whether the bill would make it to the Senate floor.

House lawmakers approved legislation in December to loosen gun regulations to allow those with permits to carry concealed weapons to legally travel with those firearms to other states.

Cornyn said in December that merging the gun bills complicated the path forward in the Senate and suggested splitting off the background check fix.