Senate Republicans on Wednesday will get a chance to go on offense on the issue of U.S. spying and surveillance, one day before Democrats are expected to press former FBI Director James Comey on what he knows about President Trump's possible ties to Russia.

The two parties have been pursuing these two different tracks since the beginning of Trump's administration, when Democrats pointed to press leaks as evidence that Trump and Russia colluded to defeat Hillary Clinton in last year's election. Trump's camp immediately focused on the leaks as a sign of possible illegal activity from Obama administration holdovers.

Today's Senate Intelligence Committee hearing on the Foreign Intelligence Surveillance Act, or FISA, will let Republicans explore their many complaints about how surveillance is conducted, how the information being gathered is dispersed, and the extent to which Trump might have been wronged. Democrats, meanwhile, will likely pursue new reports that say the president asked top intelligence officials to help him get then-Director Comey to back off the investigation into Trump's short-lived national security advisor Mike Flynn.

Over the last few days, Republicans have indicated there are several issues they might explore.

The four panelists, acting FBI Director Andrew McCabe, National Security Agency Director Mike Rogers, Deputy Attorney General Rod Rosenstein, and DNI Director Daniel Coats will almost certainly face tough questions on illegal leaks of information gathered through FISA. The most concrete evidence of that is the leaked transcript of a call between Flynn and Russian Ambassador Sergei Kislyak. That leak ultimately led to Flynn's firing by the White House.

Despite asking numerous times, the FBI still hasn't told members of Congress definitively whether it is actively investigating the source of some of that leak and others. If the intelligence community can't provide reassurance that leakers can be caught, that raises political problems for the FISA legislation that allows the surveillance to happen in the first place.

At the end of this year, Section 702 of the FISA laws, which allows for foreign surveillance, will expire. If Republicans aren't convinced that leaks from that surveillance can't be contained, it could make it hard for GOP lawmakers to agree to an extension.

Another question Republicans could raise is the federal government's policy on "unmasking," which refers to decisions to reveal the names of U.S. citizens who get swept up in the surveillance of foreign targets. While officials agree that there are legitimate reasons to unmask people in some cases, Republicans allege that some Trump administration officials were unmasked in order to surveil them and that information on those targets was then leaked to make the administration look bad.

Bloomberg reported that former President Barack Obama's former national security adviser, Susan Rice, had higher-than-usual unmasking requests last year, sometimes seeking the unmasking of names of Trump associates. And currently the House Intelligence Committee has a subpoena out to find out more about the specifics of Rice's unmasking activity.

Even Sen. Lindsey Graham, R-S.C., has said that he believes his identity may have been unmasked but didn't specify when and didn't say that the unmasking was related in any way to the Trump campaign.

A recently declassified document from the FISA court could also figure prominently into the questioning at Wednesday's hearing. The FISA court is the secret court that approves requests to conduct surveillance activities, but it also provides oversight. The document revealed that numerous searches for internet data weren't following the strict guidelines required by law, meaning many Americans were illegally or improperly surveilled. In that document, the court said the issues raised "a very serious Fourth Amendment issue" about intelligence illegally collected by the intelligence community that appeared to be at a peak in 2016.

Republicans may be encouraged by this week's news that the FBI arrested one suspected leaker of classified documents. Reality Winner, a young contract worker in Altanta, allegedly sent classified documents to the news outlet The Intercept and was arrested shortly afterward.

Winner's arrest has also produced a different kind of problem on pursuing leaks. Some have suggested it's odd that leakers outside the intelligence community can be tracked down and arrested quickly, while leakers inside the agencies themselves are rarely discovered and prosecuted, as radio host Hugh Hewitt suggested in a recent interview with Senator Tom Cotton of Arkansas.

It was the first procedural victory for a Trump administration that has been arguing for months that the main storyline here is the damaging and likely illegal leaks against the government, not President Trump's alleged and so far unproven ties to Russia.