Gaitán is... a bit of a controversial figure in Colombian historiography. Since Gaitán was a populist figure who didn't make it to the Presidency, we are only completely sure about two things about his political ideals:
a) he was strongly populistic, and
b) he was a member of the Liberal Party, and in the left wing of said Party (though not as far as sympathising with the PCC)
That being said, Gaitán would almost certainly cruise to victory in 1949. His ability to mobilise people, even when not even radio was strongly distributed across the country, was incredible. And Gómez, the Conservative candidate, was a literal Fascist who tried to instate a Corporatist change to the Constitution, supported a Night of the Long Knives, and was hideously unpopular. "Laureano" is still a term for "far-right" here; no way he wins. The only reason he won iOTL is that the Liberals, shocked by the violence of the Bogotazo and threatened by Gaitán's death (which back then was thought to be ordered by the Conservatives) launched no candidate.
So probably a more fiery version of Alfonso López Pumarejo's Marching Revolution, which coopted syndical movements to greatly reform the Constitution. Our Constitution in the XXth Century was radically conservative, so it wouldn't be very odd to see Gaitán ask for a Constituent Assembly and the creation of a more social-democratic Constitution. Whether that's successful is up for anybody's guess.
Gaitán would almost certainly also look for land reform to a greater degree than the 1930s Liberal governments achieved - they
tried, but it wasn't really successful because Ospina and Gómez' ultra-Conservative governments managed to roll back those reforms very effectively. It's possible that land ownership for thousands of middle-class and some lower-class peasants becomes a possibility; that makes me kinda giddy inside, since land ownership has been the lower classes' perpetual unheard cries.
Now, regarding U.S. intervention, it's certainly possible that the U.S. stands by since Gaitán was pretty strongly anti-Communist, but it's also possible that syndicalist support and land reform threatens US interests in regards to fruit companies. They almost intervened in 1928, which triggered the
Banana Massacre. So I'm putting 50/50 chances on history going like OTL, with Gaitán deposed and a far-right government starting La Violencia and then leading to a military coup by Liberal elements in the military (what Rojas Pinilla - the closest thing we had to a Perón - did) or Gaitán managing to pass further reforms like López Pumarejo did.
How will those reforms turn out in the hyperpolarised climate of 1950s Colombia I don't know. Now, the situation regarding La Violencia is probably greatly improved by the military and the police not acting as the Conservative Party's personal paramilitary forces iOTL, and it's possible that a Gaitán presidency and the lack of a Gómez presidency keeps a lot of peasants from flocking to guerrilla groups. But conversely, many other places could've launched Conservative guerrillas, so maybe instead of proto-FARC causing violence in Tolima and the coast we'd have a proto-AUC causing violence in Antioquia and Cundinamarca.
In regards to Gaitán becoming a strongman, Colombia's institutions, partisan and State, were relatively strong after the 1886 Constitution, and I'd doubt that Gaitán alone could tear down those institutions and instate as great a grasp on the Colombian government as Perón did in Argentina. However, it's almost assured that something like
Peronismo pops up in Colombia in the name of Gaitán - he's insanely revered as is iOTL, if he were either overthrown by the Americans or became a successful President I'm sure he'd be a political God.