Article originally appeared on CNN.com

Robert F. Bauer is a partner at Perkins Coie, former White House counsel, and former general counsel to Obama for America. Charles R. Black is chairman of Prime Policy Group and a former adviser to several presidential candidates including John McCain in 2008. Together they have co-chaired the Vice Presidential Selection Working Group at the Bipartisan Policy Center. The opinions expressed in this commentary are those of the authors.

For the presidential campaigns, beginning early and devoting adequate time to vetting and selecting a running mate has never been as important as it is this year.

Typically, a candidate's campaign begins the vice presidential nominee selection process after mathematically securing their party's nomination, and it requires at least eight weeks to be thorough. However, two factors complicate that time line this year.First, the national party conventions are being held earlier this cycle than in any other presidential election in the past 20 years. The conventions' early dates significantly shorten the window between the dates when a candidate mathematically clinches the nomination and the start of the party convention.Second, the active phase of the primary campaign in 2016 may run later than in years past. This may not leave adequate time for the vetting and selection process. And if it is unclear who a party's nominee will be going into the convention, there will be absolutely no time to follow the vetting schedule of previous campaigns.Consequently, all candidates who are still in the race eight weeks before their conventions, or essentially near the end of May this year, should begin this process in earnest.

A successful and responsible vice presidential selection requires thoroughness and care, and that means it takes time. A presidential candidate's selection of a running mate is one of the first looks at how he or she will govern. The choice of a vice presidential running mate illuminates those characteristics that are important in a partner to the presidential candidate, and the structure and process used to make the selection is a glimpse into the candidate's management style.The choice of a running mate obviously involves political considerations, such as its appeal to certain communities, states or wings of the party. But these political considerations are necessarily weighed along with -- and sometimes against -- the potential vice presidential nominee's readiness and qualification for the second-highest elected office.

The modern vice president is a close adviser and confidante to the president, typically assigned important White House initiatives. The vice president must also, of course, be able to step into the nation's highest office if the president is unable to fulfill his or her term.

Over the past five months, we chaired a bipartisan group of 10 advisers to previous presidential campaigns to develop the principles and best practices that would govern an effective vice presidential selection process. Our recommendations are simple and direct, and the time crunch -- the need to get started now -- is not our only concern.

Presidential nominees are well-served by getting to know the potential vice presidential candidates personally. One key approach is for the campaigns to arrange for possible running mates to join the nominee on the campaign trail. The ticket is a short-term political alliance but also a longer-term personal and governing partnership, and of crucial importance is the element of personal compatibility and mutual confidence.

Other recommendations concern the running of a well-designed and efficient selection process. Among them are that the campaigns should take steps to assure that the sensitive task of vetting candidates should be tightly structured to assure confidentiality. This requires limiting the circle of those provided with the information and requiring all involved to sign nondisclosure agreements.

These measures encourage qualified candidates to put themselves forward for consideration and to engage candidly with the vetting process. It also guards against the risk that the wider circulation of vetting material could adversely affect trust and working relationships within the nominees' senior ranks and reduces the chance that, after the campaign, sensitive data could be put to inappropriate use.

Our group also concluded that the process must be conducted by professionals with the appropriate skills. In the past, it has often been led and conducted by lawyers, typically with the capacity to draw on the resources of their law firms, to review public records and conduct interviews.

Not all lawyers are experienced in this kind of background research, however, and campaigns should identify those whose practices and experience have given them some knowledge of the effective use of available resources to conduct sensitive research. Increasingly important is sophistication in tracking information found on social media and elsewhere on the web.

It is an extraordinary feature of our political system that the selection of a vice president, a decision of great magnitude, is left almost entirely in the hands and to the personal judgment of the presidential candidates. A thorough and successful vetting requires the campaigns to invest significant time, effort and resources. The decision made will have a lasting impact not just on the campaign, but on the country as well.