Hillary Clinton, Democratic front-runner. (Justin Lane / Andrew Gombert/European Pressphoto Agency)

The presidential candidates in both parties are still in the throes of their nomination contests, but a new report authored by veterans of past campaigns and conventions offers a clear warning to them all: If you haven’t already done so, start your vice-presidential selection process now.

Already, some of the campaigns have made preliminary steps to begin that process, but none appears very far along. As a result, two suggestions in the report are notable, given time pressures that could affect this year’s selections. One is to avoid any last-minute vetting of prospective candidates. The other calls on candidates to carve out time well ahead of their decision to get to know their prospective running mates.

The report, issued under the auspices of the Bipartisan Policy Center, concludes that the process of vetting and selecting a vice-presidential running mate takes a full eight weeks. With the two political conventions convening in mid-to-late July, rather than at the end of August or early September as in the past two presidential elections, that suggests that the candidates are already up against the clock.

The report highlights the significance of picking a running mate. As recent vice presidents have played more central roles in presidential administrations, the process of picking them has become somewhat more orderly — but not always. The process remains in the hands of individual candidates with their own idiosyncrasies and political needs.

Paul D. Ryan, left, and Mitt Romney chat aboard their campaign plane during the 2008 election. (David Goldman/Associated Press)

The goal of the new report is to establish clearer standards for the process of narrowing a potentially long list of contenders to a short list of four or six finalists and eventually to a running mate. “Selecting a vice president is one of the most important decisions a presidential candidate will make,” the authors say. “The consequences of the selection could prospectively extend beyond the campaign and have a lasting impact on the country.”

Given the unsettled state of the Republican race in particular, the panel said the process should begin even in the absence of a presumptive nominee. “The key consideration is timing, not whether the likely presidential nominee has emerged,” the report states. “If the race is still not decided, the candidates still in contention should launch their vetting processes so that they have the eight weeks minimum for an adequate vetting.”

On the question of hasty vetting, the group says this: “Candidates should recognize the risks of vetting under these pressures. Consequently, they should adopt as a rule of thumb that with the appropriate resources, a short list of vice presidential nominees requires eight weeks for anything approaching a thorough vetting.”

In 2008, Sen. John McCain turned late in the process to then-Alaska Gov. Sarah Palin when other options fell through. As a result, the final stages of the vetting process were rushed. McCain did not meet with Palin for a serious conversation until the day before she was unveiled to the public, and she did not undergo final stages of vetting until the night before that.

On the issue of getting to know their running mates long before they make a selection, the report highlighted what Mitt Romney did in 2012. He brought potential running mates onto the campaign trail with him both to gauge their political skills and as a way to get to know them better. His chemistry with current House speaker Paul D. Ryan was instantly obvious to Romney advisers and contributed to his selection.

Other presidential candidates have done this part of the process in a far less public way, using elaborate means to avoid detection of any meetings between the presumptive nominee and prospective candidates.

The report also highlights the sensitive nature of the vetting process and the risk that financial, medical or other personal information could fall into the wrong hands or be leaked to the press. The collection of personal data draws in part from a lengthy questionnaire that can run to 70 questions or more, many of them highly intrusive. New questions have been added year by year as new kinds of scandals involving politicians have been disclosed.

Barack Obama and Joe Biden take the stage in Springfield, Ill., during the 2008 election. (Linda Davidson/The Washington Post)

Notably, the panel urged presidential candidate to restrict access to this information to as small a number of people as possible and says all of them should be required to sign non-disclosure agreements.

More significantly, the group recommends keeping most of the campaign’s political advisers far away from the process. One reason is to avoid interference and potential conflicts of interest by strategists who have clients who are under consideration. The other concern is that potentially damaging information would be used against one of the contenders in a future campaign.

“It is in the interest of both the campaigns and political staff to place strict limits on political staff’s access to the most sensitive, raw information obtained in the vetting process,” the authors conclude.

The authors are keenly aware of the risk of this kind of information becoming public, despite assurances to those under consideration that it will be kept confidential. The report’s authors say there must be plans for destroying data after the process ends and that when senior political advisers are briefed on the outcome of the process, all sensitive information should be shared verbally rather than with a written report.

Typically, teams of lawyers carry out the vetting process. The new report notes that in the age of social media, lawyers might not be the most skilled at plumbing the social-media activities of prospective candidates.

“Online activity is a case where the expertise required to vet this space might exceed the in-house capacities of the campaign,” the report states. “Specialized consultant services would serve the campaign’s interest in both thoroughness and expedition.”

The final series of recommendations includes suggestions for notifying the running mate and those who were not picked and for the public rollout. The report says the new team should go slow in giving interviews to the media.

“Even the most experienced vice presidential nominee will need several days of interacting with the campaign organization and the presidential nominee to get up to speed on all of the priorities of the nominee and of the campaign, before he or she is prepared to fully interact with the press.”