Amid all the uncertainty in the debates over guns and immigration is a snapshot of the state of play on both fronts. His name is Marco Rubio.

Sen. Marco Rubio (R-Fla.) (Alex Wong/Getty Images)

For either gun control or immigration reform to pass, the reality is that Democrats need to persuade at least some Republicans in Congress to join them.Thus, the Florida Republican senator’s posturing on the issues is well worth watching. As a potential presidential candidate who must mind his every move, Rubio is both a good barometer of what’s politically palatable for much of his party, as well someone who can entice others to follow his lead.

Let’s first take a look at immigration. Rubio belongs to the so-called “Gang of Eight” senators working to develop a broad package of reforms. The fact that he and other Republicans are involved in the talks illustrates a political reality that has been crystal clear since the 2012 election: Having performed poorly at the polls among Hispanic voters, many Republicans are embracing immigration reform to reach out to a growing share of the electorate the party can no longer afford to alienate.

Where Rubio ends up on the issue will say even more. The group appeared to have cleared its final policy hurdle when business and labor leaders agreed to terms on a new guest-worker program late last month. But Rubio quickly warned that a deal wasn’t done just yet. And until he signs off on a final measure, the possibility that he walks away will live on.

Rubio’s pause reflects a broader sentiment in the GOP right now. Sure, immigration reform is a political necessity, but caving in to Democratic demands and embracing new laws conservatives will grouse about is politically perilous too — especially for someone who might run for president. In other words, if Rubio is to embrace the final proposal the "Gang of Eight" comes up with, it can really only be after extended consideration, and the perception that he regularly pushed back against the Democrats in the group.

Senate Democrats should hope that Rubio sticks with the group, because the party needs more than a few Republicans to sign onto immigration reform in the upper chamber for the legislation to have any hope of passing in the GOP-controlled House.

“We don't want this bill to be, you know, 53 Democrats and just a handful of Republicans because we need broad bipartisan support, particularly to get a bill done in the House,” Sen. Charles E. Schumer (D-N.Y.) said Sunday on CBS News’s “Face The Nation.” Schumer is part of the “Gang of Eight."

And Rubio isn’t just any Republican. Beloved by conservatives and the establishment alike, a Rubio seal of approval would bring with it valuable rank and file votes because he’d instantly provide political cover to wavering Republicans.

"Marco is all the passion, energy and drive of the emergent conservative movement with none of the rough edges of some of the Tea Party candidates who flamed out at the ballot box," said Florida-based Republican strategist Rick Wilson.

On the issue of guns, Rubio’s position is also telling. He’s joined a group of conservative senators who’ve threatened to filibuster Democrats’ gun control legislation. And when well-known senators like Rubio and Sen. Rand Paul (R-Ky.) are threatening to filibuster gun control, it applies pressure on other Republicans who take a cue from them. Consider that the initial list of three senators who were threatening to filibuster has grown to 13, including Rubio.

Rubio's position on guns also reflects the broader political difficulty of passing new gun-control laws. It’s been difficult for gun-control advocates in the Senate to win wide support from their colleagues, even as polls show the public overwhelmingly favors expanding background checks, which is at the center of the debate over guns.

From a political perspective, Rubio’s actions reflect both the state of play and where it’s probably headed. He’s both leader and follower. He can’t afford to stray too far from what much of his party has already decided (guns). And where it hasn’t decided, many Republicans will look to him before they make their next moves (immigration).

Rubio’s positions are also reflective of another reality of rising through the ranks in politics: To succeed, pick the spots where you want to stand out.

Rubio clearly wants to make a mark on immigration. He’s the most prominent Hispanic politician in the Republican Party. If reform efforts are successful, he’ll have a high-profile policy achievement on which to stand – and potentially run for president.

When it comes to a potential gun filibuster, the picture is a bit different. It was a trio of other senators – including Paul, another potential presidential candidate – who first raised the issue. Rubio agreed to join the effort later. Once again, the leader and follower dynamic is at play. It would be politically foolhardy for Rubio not to join in, lest he potentially fall victim to attacks from Paul’s allies that he wasn’t conservative enough on guns, if they both run for president in 2016.

Predicting how the debates over guns and immigration will turn out in Congress is part-guessing game right now, with so many variables and moving parts in the talks. But for some degree of clarity on it all, keep an eye how the junior senator from Florida is positioning himself.